Ab initio study of optical excitations: Role of electron-hole interaction

Abstract

An ab initio approach to calculating the optical absorption spectrum and exciton states in real materials is discussed. The approach is based on evaluating the one-particle and the two-particle Green’s function for the quasiparticle and optical excitations, including relevant electron self-energy and electron-hole interaction effects from first principles. The method has allowed the calculation of the continuum absorption spectrum, as well as, the discrete bound exciton states for a range of materials. Results are presented for bulk semiconductors and insulators, surfaces, conjugated polymers, and small clusters. In many of these systems, the electron-hole interaction is shown to strongly alter the excitation energies and the optical spectra. The nature of bound and resonant exciton states are also discussed.